# std::wstring_convert<Codecvt,Elem,Wide_alloc,Byte_alloc>::to_bytes

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< cpp‎ | locale‎ | wstring convert

Defined in header `<locale>` |  |
byte_string to_bytes( Elem wchar ); | (1) |
byte_string to_bytes( const Elem* wptr ); | (2) |
byte_string to_bytes( const wide_string& wstr ); | (3) |
byte_string to_bytes( const Elem* first, const Elem* last ); | (4) |

Converts a wide sequence to a byte string using the facet pointed to by `cvtptr`﻿.

1) The wide sequence only consists of one element byte.
2) The wide sequence is the null-terminated sequence beginning at ptr.
3) The wide sequence is the sequence contained in str.
4) The wide sequence is the range `[`first`,` last`)`.

Before the conversion begins, if *this was not constructed with constructor overload (3), `cvtstate` will be set to its default value (the initial conversion state).

The number of input elements successfully converted will be stored in `cvtcount`﻿.

### Return value

If the conversion succeeds, returns the conversion result. Otherwise, if *this is constructed with constructor overload (4), returns `byte_err_string`.

### Exceptions

If the conversion fails and *this was not constructed with constructor overload (4), throws std::range_error.

### Example

Run this code

    #include <codecvt>
    #include <iomanip>
    #include <iostream>
    #include <locale>
    #include <string>

    // utility function for output
    void hex_print(const std::string& s)
    {
        std::cout << std::hex << std::setfill('0');
        for (unsigned char c : s)
            std::cout << std::setw(2) << static_cast<int>(c) << ' ';
        std::cout << std::dec << '\n';
    }

    int main()
    {
        // wide character data
        std::wstring wstr = L"z\u00df\u6c34\U0001f34c"; // or L"zß水🍌"

        // wide to UTF-8
        std::wstring_convert<std::codecvt_utf8<wchar_t>> conv1;
        std::string u8str = conv1.to_bytes(wstr);
        std::cout << "UTF-8 conversion produced " << u8str.size() << " bytes:\n";
        hex_print(u8str);

        // wide to UTF-16le
        std::wstring_convert<std::codecvt_utf16<wchar_t, 0x10ffff, std::little_endian>> conv2;
        std::string u16str = conv2.to_bytes(wstr);
        std::cout << "UTF-16le conversion produced " << u16str.size() << " bytes:\n";
        hex_print(u16str);
    }

Output:

    UTF-8 conversion produced 10 bytes:
    7a c3 9f e6 b0 b4 f0 9f 8d 8c
    UTF-16le conversion produced 10 bytes:
    7a 00 df 00 34 6c 3c d8 4c df

### See also

from_bytes | converts a byte string into a wide string (public member function)
wcsrtombs | converts a wide string to narrow multibyte character string, given state (function)
do_out [virtual] | converts a string from `InternT` to `ExternT`, such as when writing to file (virtual protected member function of `std::codecvt<InternT,ExternT,StateT>`)

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